A more and more important consumer need, which underlies development in the absorbent article field, in particular catamenials, is the provision of products with higher comfort level during use.
One means for providing consumer comfort benefits in absorbent articles is by the provision of breathable products. Breathability has typically concentrated on the incorporation of so called ‘breathable backsheets’ in the absorbent articles. Commonly utilized breathable backsheets are microporous films and apertured formed films having directional fluid transfer as disclosed in for example U.S. Pat. No. 4,591,523. Both these types of breathable backsheets are vapor-permeable allowing gaseous exchange with the environment. This thereby allows for the evaporation of a portion of the fluid stored in the core and increases the circulation of air within the absorbent article. The latter is particularly beneficial as it reduces the sticky feeling experienced by many wearers during use.
However those skilled in the art are faced with several problems when providing absorbent articles with high breathability. An important drawback associated with the use of breathable backsheets in absorbent articles is the negative effect on the protection level performance, by leakage known as wet through onto the users garment. Although, breathable backsheets in principle only allow the transfer of materials in the gaseous state, physical mechanisms such as extrusion, diffusion and capillary action may still occur and result in the transfer of the fluids from the absorbent core through the backsheet and onto the users garments. In particular, these mechanisms become more dominant if the article is utilized during physical exertion, or for heavy discharge loads or over extended periods of time.
Another need when providing breathable absorbent articles, especially highly breathable absorbent articles, is the control of odorous compounds within the articles.
Malodorous compounds typically present in absorbent articles originate from a number of sources. Firstly, the components of the fluid discharge such as urine, perspiration, lactational fluid, menstrual fluid and blood may themselves contain malodorous compounds. Secondly, malodorous compounds may be generated as a result of the degradation of the components of the fluid discharge. Thus there are a wide range of compounds, which may be present at some time during the use of an absorbent article, which have an associated malodor.
It is believed that due to the very nature of a breathable absorbent article, malodorous compounds contained therein may, similar to air and vapor, be more readily exchanged with the environment. Hence, the malodorous compounds are able to escape from the article and are dissipated into the surroundings. Consequently, it is at least perceived by a number of potential users of absorbent articles that malodorous compounds are more easily detectable from breathable absorbent articles than from non-breathable absorbent articles. The presence and detection of malodorous compounds from absorbent articles is however highly undesirable and may cause the wearer of these articles extreme embarrassment and thus, the prevention of their detection is highly desirable.
Another main problem with breathable absorbent articles is that they function well upon initial use while their breathable properties, especially their air transmission abilities, are drastically decreased upon initial loading these articles with bodily fluids. Since loading these articles with liquid is the ultimate reason for their existence a problem underlying the present invention is to maintain a minimum breathability from the wearer surface of the product through the backsheet during the usual usage period.
It is hence an object of the present invention to identify disposable absorbent articles, which maintain their breathability, especially their air transmission ability, preferably above a critical level, even after loading of the articles. It is further an objective of the present invention to provide this continued performance benefit without impairing on the basic absorption and liquid retention functions of such articles. Yet it is an object of the present invention to provide absorbent articles having not only an initial high comfort level but also effective comfort level upon prolonged wearing time of the articles while providing a high level of protection and effective odor control towards a broad spectrum of malodorous components.
It has now been found that these objects are achieved by providing a breathable absorbent article, particularly by the provision of a breathable backsheet, which article comprises a chitosan material. It has only now been found that the use of chitosan materials in disposable breathable absorbent articles can provide an unexpected benefit in respect to maintaining effective breathability of the articles during prolonged usage conditions.
Chitosan materials have the ability to instantaneously reduce fluid diffusion once they are contacted with bodily fluids, thereby concentrating the storage of acquired fluid in their close proximity. This reduction of internal liquid transport results in reduced surface area of the absorbed fluid (e.g., reduced surface area of the stains of menses in the articles). In other words the presence of a chitosan material in an absorbent article will result in larger area of dry article (pad), which is not soiled by bodily fluids like menses. Advantageously the concentration of the bodily fluid at limited locations on the article will maintain the overall breathability of the article at higher level in comparison to the same article subjected to the same amount of bodily fluid but wherein the bodily fluid is left to diffuse over bigger surface area.
Without to be bound by any theory, this benefit is obtained due to the properties of chitosan material to instantaneously gelify bodily fluids coming into contact with it. The gelification rate of chitosan material is only a few seconds towards bodily fluids, i.e., organic fluids like menses. The positively charged cationic groups of the chitosan materials will interact with negatively charged anionic functionalities present in bodily fluids, like the carboxylic groups of proteins or hydroxylic groups of short chain acids (e.g., butyric acid). This will result in the formation of tri-dimensional net between cationic function of the chitosan materials and such molecules with anionic groups. This rapid physical change of the bodily fluid will instantaneously immobilize it in the article avoiding fluid transfer.
Advantageously the presence of chitosan material, alone or in combination with an anionic absorbent gelling material like polyacrylate, allows to maintain the breathability of the whole article at higher levels as compared to a same article (in structure and materials) which comprises for example only such an anionic absorbent gelling material in absence of chitosan material at the same total level.
The purpose of the present invention is preferably achieved when the breathability of an absorbent article as measured by the air permeability of the article expressed in l/m2/s, after absorption of 2 ml of artificial menstrual fluid, is maintained to provide at least 35%, preferably at least 45%, more preferably at least 55% of the air permeability of the dry absorbent article.
The artificial menstrual fluid is described in details herein after. The artificial menstrual fluid in this comparison is entered in the center of the article. Air permeability (that is the capacity of an absorbent structure to exchange/circulate air) is measured in accordance with the air permeability test disclosed herein after.
By selecting chitosan materials and using them in breathable absorbent articles not only improved physical comfort to the user during use is provided but also reduction or even prevention of the formation of malodor as well as increased level of protection are provided. Advantageously it has been found that one single ingredient used in an absorbent breathable article combines the three benefits of improved comfort during use, malodor reduction over a broad range of malodors compounds and leakage/wet through reduction.
Without to be bound by any theory it is believed that chitosan materials provide fluid absorption and odor control of malodorous components associated with bodily fluid by multiple mechanisms.
Firstly, the odor and fluid absorption and retention characteristics of chitosan materials due to the presence in the polymer structure of ionisable cationic functional groups. These groups are usually ammonium groups, a high proportion of which are in the salt form when the polymer is dry but which undergo dissociation and salvation upon contact with bodily fluid. In the dissociated state, the polymer chain will have a series of functional groups attached to it which groups have the same electric charge (e.g., —NH3++H3N—) and thus repel one another. This leads to expansion of the polymer structure, which, in turn permits absorption of molecules (malodor and fluid).
Secondly, the positively charged cationic groups of the chitosan materials will interact with negatively charged anionic group-bearing molecules present in bodily fluids, like the carboxylic groups of proteins or hydroxylic acid bearing entities like short chain acid (e.g., butyric acid) and thus forms tri-dimensional net which will entrap most molecules (like lipids, acids) thereby retaining fluid and malodor.
Thirdly the chitosan materials are believed to act as antimicrobial agents. Indeed the chitosan material with its positively charged cationic groups will interfere with negatively charged surface of microorganism walls, thereby inhibiting the growth of such microorganisms or even killing such microorganisms. The chitosan material will also interfere with negatively charged surface of enzymes, thereby inactivating the enzymatic activity, which, like the microbial activity, are otherwise responsible for the formation of malodorous components. The chitosan materials further act by their indirect antimicrobial activity by linking some of the microorganism nutriments like lipids and/or minerals, this by their chelating properties.
It is believed that the breathable environment does not only deliver the primary comfort benefit but also contributes to the effective odor prevention benefits associated with the articles according to the present invention. Indeed the breathability of the article, which reduces the hot, humid and anaerobic environment between the skin of the wearer and the surface of the absorbent article, contributes in an overall reduction of growth of microorganisms, thereby reducing the presence of pathogen organisms in the bodily fluid.
The reduction in the hot, humid and occlusive environment between the vicinity of the skin of the wearer and the article itself also reduces the tendency of the wearer to perspire. Consequently, the amount of associated perspiration related odor will be reduced. Thus, the breathability of the article actually reduces the amount of odor generated within the absorbent article.
In a particularly suitable embodiment of the present invention the chitosan material is located in the core of the absorbent article directed towards the backsheet (i.e., in the core but in closer proximity to the backsheet than to the topsheet) or in the backsheet itself (e.g., the secondary backsheet). Such executions allow to best combine the needs of highly breathable absorbent articles and reduction or even prevention of odor and fluid leakage through the breathable backsheet.
Advantageously the use of chitosan material is compatible with skin safety. Indeed, the cationic properties of chitosan materials allow binding to the negatively charged surface of the skin, typically in the case of rewetting occurrence (where chitosan can be brought in contact with the skin trough bodily fluid transport), thereby moisturizing the skin and providing a long lasting softness and fullness.
Also chitosan material has been found to be particularly suitable for absorbent articles like breast pads as an effective material for absorbing lactational fluids. Indeed the use of chitosan material in breast pads/nursing pads provides effective fluid absorption towards lactational fluids, i.e. fluids containing a high proportion of electrolytes and proteins that typically would interfere with usually used gelling absorbent materials like polyacrylates. Also the antimicrobial activity of chitosan material will prevent the formation of skin irritation or even breast infection while being safe to babies. Thus in its broader aspect, the present invention also encompasses nursing pads comprising chitosan material.